1. Field of the Invention
This invention relates to chiral phospholanes derived from natural products, and asymmetric catalysis using these phospholanes.
2. Description of Related Art
Many chiral phosphine ligands have been explored for practical application in asymmetric catalysis, but few chiral ligands or motifs are efficient for the synthesis of commercially useful chiral molecules in industry.
Among known chiral phosphines, several are made from electron-donating chiral phospholanes. One example is the Brunner phospholane shown below. Brunner, H., Organometal. Chem. (1987) 328, 71. However, poor enantioselectivities were observed. 
The ligands DuPhos™ and BPE have been used effectively for certain asymmetric hydrogenation reactions. See U.S. Pat. Nos. 5,329,015; 5,202,493; and 5,329,015; Burk, M. J., J. Am. Chem. Soc. (1991) 113, 8518; Burk, M. J., J. Am. Chem. Soc. (1993) 115, 10125; Burk, M. J., J. Am. Chem. Soc. (1996) 118, 5142. These ligands, however, are not effective for some other asymmetric reactions. Moreover, synthesis of these ligands can be difficult, involving a tedious Kolbe reaction. Also, several liquid DuPhos™/BPE ligands are air-sensitive and therefore difficult to handle. 
The chiral phosphine RoPhos and its use in Rh-catalyzed asymmetric hydrogenation have been reported. Holz, J. et al., A. J. Org. Chem. (1998) 63, 8031; EP 0889 048. Chiral phosphine X1 has also been reported. Carmichael, D. et al., Chem. Commun. (1999) 261. However, the synthesis is tedious, involving a P stereogenic center.
The inventor has found that it was not possible to make hydroxy analogs of RoPhos using the experimental procedure disclosed in J. Org. Chem. (1998) 63, 8031. A new synthetic route has been developed. Unique properties are associated with hydroxylphospholanes. An efficient route to these compounds has also been developed by this inventor. Based on this hydroxylphospholane framework, a polymer chain or a soluble species such as SO3−, PO32−, (CH2CH2O)nCH2CH2OH (n=1, 2, 3) can be introduced.